Airplane propeller



Oct. 24, 1933. s n-H ET AL 1,931,710

AIRPLANE PROPELLER Filed July 6, 1932 Patented Oct. 24, 1933 AIRPLANE PROPELLER Joseph B, Smith'and James H. Smith,

1 Emporium, Pa. 7

Application July 6, 1932. Serial No. 621,090

7 Claims. (01. 170-162) This invention relates to improvements in air screws or propeller structures for use primarily upon airplanes and pertains particularly to a propeller having oscillatably mounted blades.

The primary object of the present invention is to provide. a propeller structure having the blades thereof mounted for oscillatory movement and so designed that when the propeller rotates at or above a certain speed the blades will be automatically oscillated from a normal to a lesser pitch in order that they may cut more thinly into the air and thus obtain a lesser bite therein and obtain a higher rate of engine speed to increase the pulling power of the motor. 7

, Another object of the invention is to provide a propeller structure having the blades oscillatably mounted for the purpose above described, and having the blades so designed as to obtain or .bring about the desired movement thereof through the pressure of the air upon each blade at one side of its longitudinal center or its center of oscillation.

A still further object of the invention is to provide a propeller structure having blades mounted for automatic adjustment in accordance with the speed of rotation of the drivingvshaft or the advancing speed of the airplane and having associated therewith means for normally urging the blades to oscillate to a normal pitch position, or in other words, to a position where the side faces areshifted more to a position where they oppose the rotary movement of the propeller when the same is rotating at a slow speed or when the plane speed increases beyond the speed which it is caused to move through the pulling action of the propeller, as when descending or gliding.

The invention will be best understood from a consideration of the following detailed description taken in connection with the accompanying drawing forming part of this specification, with the understanding, however, that the invention is not confined to any strict conformity with the showing of the drawing but may be changed or modified so long as such changes or modifications mark no material departure from the salient features of the invention as expressed in the appended claims. I

In the drawing:

Figure 1 is a view in elevation of a propeller structure according to the present invention;

Figure 2 is a sectional view on an enlarged scale taken on the line 2-2 of Figure 1 through the center or hub portion of the structure;

Figure 3 is a view in front elevation of the hub portion of the propeller structure from which the cone cap has been removed;

Figure 4 is a sectional view taken on the line 4-4 of Figure 2.

Referring now more particularly to the draw- 9 ing wherein like numerals of reference indicate corresponding parts throughout the several views, the numeral 1 indicates generally the hub portion of the propeller structure while each of the blades is indicated generally by the numeral 2.

The hub portion 1 comprises a casting 3 which is generally fiat and of circular formation, as illustrated in Figure 3 and which has the diametrically oppositely directed sleeve portions 4. Each of these sleeve portions 4 is split inwardly Q at one point from its. edge, as indicated at 5 and each is interiorly screw-threaded as indicated by the numeral 6.

Formed integrally with the casting 3 upon the axial center thereof is a hub'sleeve 7 which opens at its ends through the front and rear faces of the casting and is designed to receive the tapered forward end portion 8 of the airplane engine shaft. This forward end portion 8 of the engine shaft is reduced and screw-threaded as indicated at 9 Q and when it is in position in the hub sleeve '7 this reduced threaded portion projects beyond the front face of the casting as shown in Figure 2 to receive the nut 10 which is drawn ,up against the face of thecasting to maintain the same in position on the shaft.

The front face of the casting 3 has formed therein the substantially annular recess 11 which opens at diametrically opposite sides into the open areas 12 which extend longitudinally of the cast- 9 ing and which are in parallel off-set relation. These recessed areas extend in the same direction as the sleeves 4, as shown in Figure 3.

The forward end of the hub sleeve 7' projects into the annular recess as shown in Figure 3 and positioned in the recess '11 and surrounding the forward end of the hub sleeve 7 is the fiat annular plate 13 which at diametrically opposite points has formed integral therewith the bifurcated arms 14, each of which lies in a recess 12; P

As shown, these arms 14 are of materially less width than the recesses in which they are positioned and they are normally retained in alignment on the longitudinal center of the casting by coil expansion springs 15. Each of these springs 1 15 is located in a suitable passage 16 in thecasting to open into a recess 12 at the side thereof. The springs 15 exert pressure upon the arms 14 of the annulus in opposite directionsand as will be seen, each arm 14 has a space between one 1 g side of it and the adjacent side of the recess 12 in which it is located so that under the proper conditions the annulus may oscillate slightly to swing the arms 14 in their respective recesses and against the tension of the adjacent holding spring The opposed annular faces of the furcations of each bifurcated arm 14 of the annulus 13 are grooved or recessed as indicated at 1'7, the pur-. pose of which grooves will be hereinafter. more fully explained.

Formed in the front face of the casting to open into each of the recess areas 12 is an aperture 18 which extends into the adjacent sleeve and in alignment with each of these apertures at the opposite side of the sleeve is a similar aperture 19.

At the inner end of each of the sleeves 4 there is located a race ring 20 forming a part of a roller bearing structure, the rollers of which are indicated at 21- and the inner ring for the hearing which rests upon these rollers is indicated by the numeral 22.

These inner rings 22 are secured about the reduced inner end portions 23 of the shanks 24 of the propellers 2, which shanks extend into the sleeves 4 in the manner illustrated. Each of the propeller blade shanks 24 is screw-threaded through a portion of its area, as indicated at 25 and about this screw-threaded area is fitted a ring nut 26. The ring nuts 26 serve to limit the inward movement upon the shaft shanks, of an inner ring element 27 of a second roller bearing structure; the rollers of which are indicated by the numerals 28. Surrounding each of the propeller shaft shanks 24 is an exteriorly threaded collar 29 which threads into the adjacent sleeve engaging the threads 6 thereof and these collars are formed adjacent their inner ends to form the outer race rings 30 against which the bearing rollers 28 position. The outer ends of the collars 29 are provided with the lateral surrounding flanges 31 which overlie the ends of the sleeves in the manner illustrated and when the collars are in the position shown the sleeves have secured thereabout in suitable annular grooves the clamping bands 32 which when drawn together by any suitable. means, as for example, by a nut and bolt, slightly constrict the sleeves and thus grip and hold the collars 29 against accidental displacement.

Each of the propeller shaft shanks 24 has secured therein the tapered end portion 33 of a pin member 34 which has a ball like head 35 which extends through the adjacent aperture 18 and positions between the two portions of the adjacent bifurcated end 14 of the annulus 13. These ball heads 35 are rotatably mounted on the ends of the pins 34 upon the reduced pin extensions 35'. Due to the size of each of the pin heads 35 with respect to the width of the opening between the portions of the bifurcated extensions, the heads snugly fit in the recesses 1'7v and are thus held against displacement through movement transversely of the members. As will be readily seen these heads must be inserted from the ends of the bifurcated members and the plate or annulus 13 then placed in position and the reduced or tapered ends of the pins at the same time extend through the openings or gapertures 18 and into the passages formed in "the shanks of the propellers in which they are located;

7 The reduced ends of the pins 34 have mounted thereon the nuts 36 which are placed in position through the openings 19.

After assembling the parts in the manner shown; and described the threaded forward end portion 9 of the shaft 8 has secured thereon the cone ,like cap 37 which covers the annulus 13 and the parts connected therewith and thus' gives a finished appearance to the propeller structure, as shown in Figure 1.

In addition to the expansion springs 15 the casting has mounted therein the two expansion springs 38 which are disposed in passages 39 arranged substantially tangentially to the annular plate 13 and the forward ends of these springs have the heads 40 thereof located in recesses 41 cut in the periphery of the annulus 13.

As shown in Figure 3 these springs are upon opposite sides of the annulus and in opposed relation so that they tend to oscillate the annulus in a clockwise direction the same as do the springs 15.

While four sets of springs have been shown for maintaining the annulus 13 in the desired position it is, of course, to be understood that the tangentially disposed ones may be eliminated if desired, by increasing the size and strength of the springs 15.

Each of the propellers 2 is formed so that its trailing edge will be out of balance with the advancing edge, or in other words, the trailing edge projects farther from the longitudinal center of the propeller than the advancing edge. This effect is accomplished by giving a relatively large outwardly bowed contour to the rear or trailing edge of each blade, as indicated by the numeral 42. It will thus be seen that as thepropeller rotates the air pressure against the projecting or rearwardly bowed portion of the trailing edge will tend to oscillate the propeller and naturally this pressure will be increased with the speed of rotation.

In operation, the propeller blades 2 are so disposed that when the propeller is stationary or rotating at idling speed the pitch of the blades will benormal or with'their faces in planes at an acute angle to the axis of rotation and in this position the springs 15 and 38 will be holding the annulus 13 with the bifurcated extensions 14 thereof extending longitudinally of the casting parallel with the propeller blade shanks.

As the speed of rotation of the propeller increases the air pressure upon the extended trailing edge portions 42 will also increase and tend to oscillate the propellers. When the'air pressure increases to the point where the tendency to oscillate the propellers overcomes the strength of the springs 15 and 38 then the oscillation will occur and the pins 34 will be swung in an arcuate path transversely of the casting to shift the bifurcated portions 14 against the tension of the springs. The pitch of the blades will thus be altered from a greater to a lesser degree and consequently the blades will obtain a lesser bite" in the air and increase the speed of the motor. As the speed of the plane picks up the air pressure upon the propellers will be lessened and then the springs will be able to exert more effect upon the plate and the pins connected therewith and will tend to swing the blades back toward a sharper pitch.

Having thus described the invention, what is claimed is r 1. In a variable pitch propeller, a body constituting a hub to receive an end of an engine shaft, a pair of diametrically oppositely directed sleeves forming a part of the body and each interiorly threaded, each of said sleeves having a slit extending longitudinally therein from its outer edge, a pair of propeller blades each having a shank positioned in a sleeve, a nut surrounding each shank and threaded into the sleeve, bearing means within each sleeve for the inserted blade shank, means about each sleeve for constricting it for tight engagement with the nut therein, and means controlling the pitch of said blades.

2. In an air screw, a body formed to provide a hub for an end of an engine shaft, a pair of diametrically oppositely directed sleeves carried by the body, a pair of propeller blades each having a shank mounted in a sleeve for oscillation therein, an annular recess formed in one face of the body concentric with the hub, a body oscillatably disposed in said recess and having a central opening concentric with the hub and oppositely directed bifurcated arms disposed in recesses in the body which open into the annular recess, the sleeves having apertures therethrough each opening from one of the last mentioned recesses to the interior of the sleeve, a pin member secured to the shank of each blade and extending through the adjacent aperture, a head rotatably carried by each pin member and slidably positioned in one of said bifurcated arms, and spring elements controlling the oscillation of the second mentioned body and constantly urging it in a direction to oscillate the propellers to normal pitch position.

3. In an air screw,':abody having a hub for the reception of an end of the engine shaft, said body further having a pair of diametrically oppositely directed sleeves, a pair of propeller blades each having a shank mounted in a sleeve for oscillation therein, an annular recess formed in one face of said body concentric with the hub, a flat annulus disposed in said recess and having oppositely directed bifurcated arms disposed in recesses in the body which open into the annular recess, the sleeves having apertures therethrough each opening from one of the last mentioned recesses to the interior of the sleeve, a pin member,

secured to the shank of each blade and extending laterally through said aperture, a head rotatably mounted upon the free end of each pin member and slidably positioned in a bifurcated arm, and a pair of spring elements encased in said body and each extending into one of the second mentioned recesses and engaging the adjacent bifurcated arm and constantly urging the annulus in a direction to oscillate the propeller blades to normal pitch.

4. In an air screw having blades adapted to oscillate to vary the pitch in accordance with air pressure developed thereon as a result of their speed of rotation, a body formed to provide a hub to receive an end of an engine crank shaft, a pair of diametrically oppositely directed sleeves forming a part of the body and each interiorly threaded adjacent its outer end, a pair of propeller blades each having a cylindrical shank portion extended into one, of said sleeves, a bearing at the inner end of each shank comprising two annuli and roller elements therebetween, an annulus of each bearing being secured to a blade shank and the "other annulus being secured to the hub body, a bearing adjusting nut surrounding each blade shank and threaded into the adjacent sleeve, the end portion of each nut being formed to provide a bearing cone, a bearing cone secured to each blade shank in opposition with the adjacent nut cone, rotary bearing elements located between each of said nut cones and the adjacent shank carried cone, and means threaded upon each shank for maintaining the bearing cone thereon in adjusted position.

5. In an air screw, a body formed to provide a crank shaft end receiving hub and a pair 01' radial sleeves, said body having a recess therein about the hub and further having a pair of radial recesses each opening into the first recess, each of said sleeves having an opening through its wall which opens into a radial recess, a pair of propeller blades each having a shank mounted in a sleeve for oscillation therein, a pin secured to each shank and having an end extending through the adjacent sleeve opening into the adjacent radial recess, a flat body mounted in the first recess to oscillate on an axis concentric with the hub, a pair of arms carried by the flat body and each disposed in a radial recess, a sliding connection between each arm and the adjacent pin, and spring means constantly acting upon the flat body to oscillate the blades to a predetermined normal pitch.

6. In an air screw, a body formed to provide a crank shaft end receiving hub and a pair of radial sleeves, said body having an annular recess in one face concentric with the hub and further having a pair of radial recesses each opening into the annular recess, each of said sleeves having diametrically opposite open-- ings through its wall one of which opens into a radial recess, a pair of propeller blades each having a shank mounted in a sleeve for oscillation therein, a pin for each shank having an end extended through the shank and having the other end extending through that opening of the sleeve leading into a radial recess, means upon the first mentioned end of each pin for retaining the pin in position, said retaining means being accessible through the other opening of the sleeve, a fiat annulus mounted in the annular recess to oscillate about said hub, a pair of bifurcated arms carried by the annulus each disposed in a radial recess, the said other end of each pin beingslidably disposed between the furcations of the adjacent arm, and spring means normally actingupon the annulus to oscillate the same in a direction to oscillate the blades to a predetermined normal pitch position.

'7. In an air screw, 9. body formed to provide a crank shaft end receiving hub and a pair of radial sleeves, said body havinga recess therein about the hub and further having a pair 0. radial recesses each opening into the first recess, each of said sleeves having an opening through its wall which opens into a radial recess, a pair of propeller blades each having a shank mounted in a sleeve for oscillation therein, a pin secured to each shank and having an end extending through the adjacent sleeve opening into the adjacent radial recess, a flat body mounted in the first recess to oscillate on an axis concentric with the hub, a pair of arms carried by the flat body and each disposed in a radial recess, a sliding connection between each arm and the adjacent pin, spring means constantly acting upon the fiat body to oscillate the blades to a predetermined normal pitch, said shaft end extending entirely through the body. and a cap secured to the extended shaft end and covering the said recesses and elements therein.

JOSEPH B. SMITH. JAMES H. SMITH. 

